1. Field of the Invention
The present invention relates to an optical inclination sensor provided in various apparatuses such as electronic cameras and robots for detecting the inclination condition of the apparatuses.
2. Description of the Related Art
Conventional optical inclination sensors using a sphere are disclosed, for example, in Japanese Unexamined Patent Publication JP-A 11-14350 (1999). FIG. 7 is a plan view showing the structure of a conventional optical inclination sensor 71 in a simplified form. FIG. 8 is a cross-sectional view taken on the line VIIIxe2x80x94VIII of FIG. 7. FIG. 9 is a cross-sectional view taken on the line IXxe2x80x94IX of FIG. 7.
The conventional optical inclination sensor includes a light emitting section 73 including a single light emitting element 72; a light receiving section 75 including a light receiving element 74 having two light receiving surfaces 74a and 74b that receive diffused light from the light emitting section 73; a holder 78 holding the light emitting section 73 and the light receiving section 75 and having two inclined surfaces 76 and 77 forming a predetermined angle with each other; a lid 79 fitted to the holder 78; and a sphere 80 serving as a detection object that moves freely on the two inclined surfaces 76 and 77 of the holder 78. The conventional sphere 80 is made of iron and has a diameter of 1.0 to 1.2 mm, and a surface roughing treatment is performed on the surface of the sphere 80.
In the conventional optical inclination sensor 71, when the holder 78 is upright without inclined, the diffused light from the light emitting section 73 is received by the two light receiving surfaces 74a and 74b, and when the holder 78 is inclined rightward or leftward, the sphere 80 moves to the end of the inclined surface in the direction in which the holder 78 is inclined, so that the light is intercepted from one of the two light receiving surfaces 74a and 74b and is received by the other of the surfaces 74a and 74b. 
The conventional optical inclination sensor 71 faces the following problem. The holder 78 only has the two inclined surfaces 76 and 77 forming the predetermined angle with each other, and the surface of the lid 79 facing the sphere 80 is a plane. Therefore, when the holder 78 is upright without being inclined, the sphere 80 is situated midway between the two inclined surfaces 76 and 77, and the two light receiving surfaces 74a and 74b both receive the diffused light from the light receiving surfaces 74a and 74b both receive the diffused light from the light emitting section 73. When the holder 78 is inclined rightward or leftward, the sphere 80 moves to the end of one of the two inclined surfaces 76 and 77, so that the diffused light from the light emitting section 73 is intercepted from one of the two light receiving surfaces 74a and 74b and is received by the other of the surfaces 74a and 74b. As described above, the optical inclination sensor 71 can detect only three conditions, namely an upright condition where the holder 78 is not inclined, a rightwardly inclined condition where the holder 78 is inclined leftward, and cannot detect a condition where the holder 78 is inverted.
Moreover, since the two light receiving surfaces 74a and 74b receive the diffused light from the light emitting section 73 when the holder 78 is in the upright condition, in the case where the optical inclination sensor 71 is provided in an apparatus frequently used in the upright condition, the light is incident on the light receiving section 75, so that a condition where current flows through the light receiving section 75 continues for a long time. This increases power consumption.
Further, since the sphere 80 used for the conventional optical inclination sensor 71 is small in mass, when the optical inclination sensor 71 is inclined, there are cases where the sphere 80 stays in contact with the holder 78 and does not move due to static electricity. Therefore, in order for the sphere 80 to easily move when the optical inclination sensor 71 is inclined, although the cost of manufacturing increases, a surface roughing treatment is performed on the surface of the sphere 80 to reduce the area of contact of the sphere 80 with the holder 78. However, the angle of inclination of the optical inclination sensor 71 at which the sphere 80 starts to move is not always the same but varies largely.
An object of the invention is to provide an optical inclination sensor capable of detecting four conditions, namely an upright condition, a rightwardly inclined condition, a leftwardly inclined condition and an inverted condition, and in which power consumption can be reduced and the variation in the angle of inclination at which the detection object starts to move is small.
The invention relates to an optical inclination sensor for detecting a condition of inclination of an object to horizontal, the optical inclination sensor comprising:
a light emitting section including a light emitting element;
a light receiving section including a light receiving element having two light receiving surfaces;
a movable detection object for adjusting a light receiving condition of the light receiving section by blocking or opening paths of light from the light emitting section to the light receiving section;
a holder for housing the light emitting section, the light receiving section and the detection object, the holder having an inner surface including surfaces parallel to, vertical to and inclined to horizontal when the holder is in an upright condition; and
a lid shaped to fit to the holder, the lid having an inner surface including surfaces parallel to and inclined to horizontal when the holder is in the upright condition and the lid is fitted thereto,
wherein the detection object is movably housed in a housing space defined by the holder and the lid, and the path of light and the movement path of the detection object are formed so that the following conditions are distinctively detectable according to a position along the movement path of the detection object in the housing space:
the upright condition of the holder;
a rightwardly inclined condition of the holder;
a leftwardly inclined condition of the holder; and
an inverted condition of the holder.
According to the invention, the optical inclination sensor can detect the inclination conditions, that is, the four conditions, namely the upright, the rightwardly inclined, the leftwardly inclined and the inverted conditions. Consequently, although in the conventional optical inclination sensor capable of detecting only three conditions, namely the upright, the rightwardly inclined and the leftwardly inclined conditions, to detect the four conditions, it is necessary to provide in the apparatus two sensors disposed so as to be relatively rotated 90 degrees from each other, in the optical inclination sensor capable of detecting the four conditions, it is necessary to provide only one sensor in the apparatus. This reduces the cost of manufacturing, and reduces the space in the apparatus necessary for mounting the sensor to reduce the size of the apparatus.
In the invention it is preferable that the path of light and the movement path of the detection object are formed so that when the holder is in the upright condition, paths of light from the light emitting section to the two light receiving surfaces are both blocked by the detection object,
when the holder is in the rightwardly or the leftwardly inclined condition, one of the paths of light from the light emitting section to the two light receiving surfaces is blocked by the detection object, and
when the holder is in the inverted condition, the paths of light from the light emitting section to the two light receiving surfaces are both opened.
According to the invention, since the paths of light from the light emitting section to the two light receiving surfaces are both blocked when the holder is in the upright condition, in the case where the optical inclination sensor is used in an apparatus used being held in the upright condition for a long time, the time for which no current flows through the light receiving element is long, so that power consumption can be reduced.
Moreover, in the invention it is preferable that the paths of light and the movement path of the detection object are formed so that when the holder is in the upright condition, the paths of light from the light emitting section to the two light receiving surfaces are both opened,
when the holder is in the rightwardly or the leftwardly inclined condition, one of the paths of light from the light emitting section to the two light receiving surfaces is blocked by the detection object, and
when the holder is in the inverted condition, the paths of light from the light emitting section to the two light receiving surfaces are both blocked by the detection object.
According to the invention, since the paths of light from the light emitting section to the two light receiving surfaces are both blocked when the holder is in the inverted condition, in the case where the optical inclination sensor is used in an apparatus used being held in the inverted condition for a long time, the time for which no current flows through the light receiving element is long, so that power consumption can be reduced.
Moreover, in the invention it is preferable that the detection object is a sphere having a specific gravity of 7 or more and a diameter of 1.2 to 3.0 mm.
Moreover, in the invention it is preferable that the detection object has a surface roughness smaller than a predetermined value.
According to the invention, the detection object is a sphere having a specific gravity of 7 or more and a diameter of 1.2 to 3.0 mm, and the surface roughness of the detection object is smaller than the predetermined value. Since this provides the detection object with an appropriate mass, the detection object is never hindered from moving by static electricity, and the variation in the angle of inclination of the optical inclination sensor at which the detection object starts to move can be reduced. Further, by the mass of the detection object being in an appropriate range, the detection object having a surface roughness smaller than the predetermined value can be used as it is and it is unnecessary to perform a surface roughing treatment on the surface of the detection object in order that the detection object easily moves, so that the cost of manufacturing can be reduced.
Moreover, in the invention it is preferable that there are four inclined surfaces in all in the inner surfaces of the holder and the lid, and when the holder is in the upright condition and the lid is fitted thereto, angles between the surfaces parallel to horizontal and the inclined surfaces and angles between the surfaces vertical to horizontal and the inclined surfaces are substantially 45 degrees.
According to the invention, the holder and the lid have a total of four inclined surfaces, and when the holder is in the upright condition and the lid is fitted thereto, the angles between the surfaces parallel to horizontal and the inclined surfaces and the angles between the surfaces vertical to horizontal and the inclined surfaces are set substantially to 45 degrees, so that the four conditions, namely the upright, the rightwardly inclined, the leftwardly inclined and the inverted conditions can be detected each corresponding to 90 degrees into which 360 degrees corresponding the entire circumference of the inner surface of the holder and the lid defining the housing space is quartered.
Moreover, in the invention it is preferable that the holder and the lid have between adjoining inclined surfaces a holding surface formed so as to range from one to the other of the inclined surfaces, and the detection object is in contact with the inner surfaces of the holder and the lid defining the housing space at two contact points, namely a first contact point in contact with an inclined surface and a second contact point in contact with the holding surface.
Moreover, in the invention it is preferable that an angle between a first axis connecting the first contact point and a center of the detection object and a second axis connecting the second contact point and the center of the detection object is substantially 45 degrees.
According to the invention, since the detection object is in contact with the inner surface of the holder and the lid defining the housing space at two contact points and preferably, the angle between the axes connecting the contact points and the center of the detection object is substantially 45 degrees which form an acute angle, when the optical inclination sensor is inclined, the detection object smoothly moves, so that the variation in the angle of inclination of the optical inclination sensor at which the detection object starts to move can be reduced.
Moreover, in the invention it is preferable that a distance between the two light receiving surfaces is set to 0.5 to 1.5 mm.
According to the invention, since the distance between the two light receiving surfaces is set to 0.5 to 1.5 mm, the size of the detection object that blocks the paths of light from the light emitting element to the two light receiving surfaces is set in a range corresponding to the distance of 0.5 to 1.5 mm and suitable for blocking the paths of light. Since this prevents the detection object from being too big, the optical inclination sensor which houses the detection object can be reduced in size. Moreover, since the size of the detection object is never so small that the mass of the detection object is small, it never occurs that the detection object does not easily move due to static electricity, so that the variation in the angle of inclination of the optical inclination sensor at which the detection object starts to move can be reduced.